An improved plasmid size standard, 39R861
Related Experiment Video
Updated: Jan 29, 2026

Homemade Site Directed Mutagenesis of Whole Plasmids
Published on: May 11, 2009
Robert A Moran1, Sashindran Anantham1, Ruth M Hall1
1School of Life and Environmental Sciences, The University of Sydney, NSW, Australia.
Abstract:
The four plasmids in E. coli 39R861 have been used as size standards for closed-circular plasmid DNA since the 1980s. However, their sizes had only been estimated. Here, the complete sequence of the 61.3 kb cryptic FII plasmid p39R861-3 is reported, and the sizes of p39R861-4, pSa and NTP168 were determined to be 155.8, 40.1 and 6.8 kb, respectively. An improved size standard, 39R861+, was created by adding two sequenced, compatible plasmids to 39R861 via conjugation. The 94.8 kb conjugative B/O plasmid p838B-R mobilised the cryptic, 2.0 kb pBuzz. The six plasmids in 39R861+ are all stably maintained.
More Related Videos
Related Concept Videos
Plasmids
Cell Size
Surface Area
Cells can take in nutrients and water via diffusion through the plasma membrane itself or through specific channels in the membrane. The area of the membrane surrounding...
Measurement: Standard Units
Standard Enthalpy of Formation
Standard Electrode Potentials
Calculating Standard Free Energy Changes

